Dental porcelain electric furnace



Sept. 22, 1931. N. THOMPSON DENTAL PORCELAIN ELECI'RICV FURNACE Original Filed Feb. 26, 1925 Patented Sept. 22, 1931 NAT THortPsoN, or cHIAGo, ILLINoIs kIDIENL'ALL IORGELAIN ELECTRIG` FURNACE Boiling o1' application Seriailo. 11;665, illedlebruary 26, 1925. This application led November-21, 1928,.

y Serial No. 321,016. Renewed- Rebruary 20, 1930.

This invention relates generally to furnaces, and more particularly to an electric furnace-for fusing porcelaindental work, the principal objects ofy my inventionl being to generally improve uponA and simplify the construction of the existing forms ofv similar electric furnace;v to provide a relatively simple, practical ande cient electric dental furnace with means whereby Ythe degree of heat Wthinthe'foven orfusing: chamber may be readily controlled and regulated and fur-V ther,v to combine with a furnace of the character referred to, a `time-controlled switch that may be manually set so as to close the electric circuit tothe'heating element within the fusing chamber and which-switch will act :automaticallyv after apredetermined intervalv of time, totopeny the circuit and thereby cut oif further production of heat Within said.

heating chamber.

With the foregoing and other ob]ects in view, my invention consists in certain. novel features of construction andarrangement of parts that willY be hereinafter more fully.

shown and described and illustrated in the accompanyingv drawings, in which F ig.`1 is a top plan View of an electric furnace of my improved construction.l

Fig. 2 is a front elevational'view of the furnace.

F ig. 3 isanenlar ed vertical section taken on the lineA 3.-3 ofgFig.. 1.

Fig. 4 is a di animatie view of the elec-V trical circuits utilized in my improved furnace. Y

Fig. 5 is arear elevational view of the clock that is utilized in connection` with my im, proved furnace and which is effective in` openingthe circuit to the heating element, and simultaneously sounding an alarm.y Referring by'numerals to the accompanying' drawings which illustrate a preferred form of my invention, designates a base plate of suitable insulating material such as compressed fibre, bakelite` or stone, and: detachably; secured to` the. underside thereof is a; shallowpan llthat servesas a housing for the electrical conductors that are arranged on-theunderside of the base.

Secured Ontopfof the rear right handportion of base 10 is a perforated wall12 -that enf` closes a substantially square space 13 and arranged. on top of said Wall 12 is a cover plate- 14 of` suitable insulating material. I

Projecting upwardly from the rear 0rtion of plate 14 is av hollowl post or standard lthrough which passes a pairof insulated. conductors 16 and 17 Conductor 16 leads from. a bindingr post 1,8.on base lO'toaI con tact button 19 that is arranged on the upper front face of post 15.

Conductor 17 leads from a switch lever pivot bolt 20 that is seatedA in base 10, to a. contact button 21 that is seated in the front face of post 18 a short` distancebelow contact button 19. The oven or heating chamber of my improved furnace is substantially cylin-f drical in form and comprises a basering. 22., preferably formed ofl fire clay, ain-inner 1ining 23 of fire clay,.a jacket 24' of asbestos` or the like that encloses. lining 23 and a4 metaly shell 25 that encloses said ring and jacket,

Embedded in the exposed facey of linin 23 is a coil 26 of platinum wire, one en thereof being connected to a contact button 27 that is arran ed on therear upper side of the shell 25,0f t e oven and thev other end of said coil 26 being connected to a contact button 28 that is located on shell 25 a short distance below ybutton 27.

Arranged on the rear side of the oven are horizontally disposed loops 29Jthat are adapt-v. ed to be slipped downwardly over the upper. portion of post 15, and when the oven is prop,- erly positioned` on said post.k buttons 27 and 28 make direct contact with buttons 19 and 21 respectively.

The work carrier of my improved furnace comprises a disk 30 of re clay or the like `that is` carried by the upper end of a rack bar 3l, and the latter being arrangedv to slide through an. opening 32 in plate 14; and through a vertically arranged tube 32a that is disposed between plates 10 and 13.

yDisk 30 is provided on its lower edge with a flange 30a, which, when said disk 1s posi.-r tioned withiny ring 22, functions asy a stop to limit the movement of said disk upwardly intothe oven.

Flange 30a is also adapted to fit snugly.

heat from the furnace chamber.

Removably positioned on the disk 30 is an Y inverted crucible 33 that serves as a support for the work that is to be baked or fused and saidV Crucible being formed of Vfire clay, alundum or the like.

Disk 30 is adapted to pass through ring 22 at the base of the oven so that the crucible 33 that supports the work occupiesthe central portion of the oven chamber.VH

Rack bar 31 is moved vertically by means of a pinion-34, the teeth'of which engage ithe teeth of said rack bar and said pinionbeing fixed on a shaft 35 that is arranged for rol. tation inisuitable' bearings on plate 14.

A disk 36 is liXed on the outer end of shaft 35 and-may be engaged by the thumb and lingers when the shaft and pinion areV rotated to raise or lower rack bar 31. Y

Arranged in the chamber within perforated wall 12 isa resistance coill 37 and connected thereto at` dierent points are conductors 38 that lead to contact points 39, thelatter being arranged in 'an arcuate row on base 10.

' Aswitch lever 40 ispivoted to bolt 20 and is adapted lto successively engage the contact points 39.

, Suitably supported on base 10 is an alarm clock 41 of the type having means that may beset so as to sound an alarm bell at the end ofV al predetermined interval of time. V "A rotating Vpart of the setting means of this clock is provided'with an insulated pin 42 which, when the alarm means is set, closes a switch on the clock, said switch Vcomprising apairof spring arms 43 that are mounted on a block of insulation 44.

-i A conductor 45 leads'from one end of coil 3.7 to one Iof the spring arms 43 and a conductor'46 leads from the other spring arm to a binding post 47 that is seated on the rear por- Y tion of base 10.

' In the use of my improved dental furnace, pinion-carrying shaft 35 is rotated to move rack -bar `31 downward, thus enabling the work to beplaced on Crucible 33 that rests on disk 30.

' vShaft 35 is now rotated to elevate the rack bar and parts carried thereby, and when 'flange 30a bears against the underside of ring 22, the work to be bakedor fused and which is arranged on top of Crucible 33 occupies a position in the center of the furnace or oven chamber (see Fig.

The alarm mechanism of the clock is new set so as to sound the alarm after the lapse such heat prevails until theend of the time re-A quired for properly baking or fusing the work, whereupon the clock releases the part that carries pin or stud 42 and, as the same moves away from the switch, the arms thereof spring apart so as to open the circuit to the heating coil within the furnace. c

Simultaneously with ,the opening of the circuit just described, the bell on the clock is sounded, thereby giving an audible signal and alarm that the baking or fusing operation has been completed. Y

To remove the work from the furnace, it is only necessary to actuate yshaft35 so as to lower the rack barf 31 until disk 30 and the work carrying Crucible have been withdrawn from the chamber` j Y Rheostat arm 40 may be adjusted on contact points 39 so vas to vary thedegree'of resistance offered by coil 37, thereby regulating the degree offheat produced within the fur-` nace chamber.

In the event that the clock becomes inoperative or the user 4`ofthe furnace desires to use same without the time interval and alarm, the line conductorthat is vconnected to binding f post 47 is connected to va third binding post 48, and from the latterV the currentpasses through a conductor-49 that'lea'ds to the contact member 39 that is located'at the end of the arcuate row.` o c f Thus it will be seen that I have provided a dental furnace that is relatively simple in structure, capable of being easily andcheap-ly produced, and whichr is very effective in perp forming its intended functions. p

The porcelain or other work t0 be baked or fused may be readily positioned Vwithin Vvthe furnace or removed therefrom, the degree of heat produced'within the furnace chamber may be accurately regulated and a simple and eh'icient time controlled switch is provided for cuttingY ofil the current to the heating coil at the termination ofY a predetermined 1elapsed time interval. f f

It will be understoodthat minor changes .in the size, form and construction of the various partsof my improved dental furnace may be made and substituted for those hereinshown and described without departing from the spirit of theinventiom'the scope of'whichis set 'forth in the appended claims: This application is a reiling of my abandoned application No. 11,665, filed February 26, 1925.

I claim as my invention:

1. In an electric dental furnace, a standard, electric conductors extending upwardly through said standard, contacts at the upper ends of said conductors and arranged externally of said standard, an oven removably positioned on said standard, which oven is provided with a heating chamber that is open at its lower end, a heatin coil within said oven around the chamber t erein, contacts on the ends of said coil, which contacts are adapted to engage the contacts on the standard and a vertically movable work carrier arranged beneath the heating chamber and adapted when moved upward to plug the open lower end thereof.

2. In an electric dental furnace, a standard, electric conductors extending upwardly through said standard, contacts at the upper ends of said conductors and arranged externally of said standard, an oven removably positioned on said standard, which oven is provided with a heating chamber that is open at its lower end, a heating coil within said oven around the chamber therein, contacts on the ends of said coil, which contacts are adapted to engage the contacts on the standard, a work carrier arranged for vertical movement beneath the heating chamber and adapted when elevated to plug the lower end of said chamber and a manually operable rack and pinion for raising and lowering said work carrier.

3. In an electric furnace, a base, a standard, an oven supported by said standard, said oven comprising an enclosed heating chamber open at its lower end, electrical heat radiating means for said chamber, and a vertically movable work carrier adapted to enter said chamber through said open lower end and having a base portion adapted to plug said open lower end of said chamber.v

4. In an electric furnace, a base, a standard, an oven supported by said standard and comprising an enclosed heating chamber open at its lower end, electrical heat radiating means for said chamber, a vertically movable work carrier adapted to enter said chamber through said open lower end and adapted to constitute a tight closure for said open lower end of said chamber, and means on said carrier fork supporting work substantially centrally of said chamber when said carrier is in operative position.

5. In an electric furnace, a base, a standard, an oven supported b said standard and comprising an enclose heating chamber open at its lower end, electrical heat radiating means within said oven for said chamber, an electrical conductor extending upwardly throu h said standard and having a portion exten ing outwardly of said standard, said radiating means having a portion extending outwardly of said oven, adapted to have separable contact with each other anda vertically movable work carrier adapted to enter said chamber through the open end thereof and to constitute a closure therefor.

6. In an electric furnace, a base, a standard, an oven supported by said standard and comprising an enclosed heating chamber open at its lower end, electrical heat radiating means within said oven for said chamber, an electrical conductor extending upwardly through said standard and having a portion extending outwardly of said standard, said radiatin means having a portion extending outward y of said oven, said portions being adapted to have separable contact with each other, a vertically movable work carrier adapted to enter said chamber through the open end thereof and to constitute a closure therefor, and means on said carrier for supporting work substantially centrally of said chamber when said carrier is in operative position.

In testimony whereof I affix my signature.

NAT THOMPSON.

said portions being iso 

